[Effect of lymphokines produced by human T-T hybridomas on the proliferation of normal and neoplastic B lymphocytes]. / Influenza di linfochine prodotte da ibridomi umani T-T sulla proliferazione di linfociti B normali e neoplastici.

Human T-T hybridomas were obtained by fusing T lymphoblasts of the azaguanine-resistant CEM-6 cell line and PHA-activated normal T lymphocytes. After 4 weeks of culture with selective media, proliferating hybrid cells were cloned by limiting dilution. Several clones were obtained and one of them (F2) was shown to secrete a lymphokine with inhibitory activity on the proliferation of an EBV-transformed B cell line, of normal B lymphocytes, as well as of mitogen activated normal T lymphocytes. The proliferation of three other cell lines (MLA-144, CEM-6 and K-562) was not affected. The inhibition of cell proliferation was not due to a cytotoxic effect. The soluble factor from F2 hybridoma was very sensitive to heat-treatment, was not inactivated by target cell adsorption and, finally, it was effective at very low concentrations (70% inhibition at 1:1,000 dilution, v/v). The suppressor activity in the supernatant from F2 hybridoma did not appear to be related to other known lymphokines.

Cytotoxic and immunotoxic effects of Fusarium mycotoxins using a rapid colorimetric bioassay.

A colorimetric MTT (tetrazolium salt) cleavage test was used to evaluate cytotoxicity of twenty-three Fusarium mycotoxins on two cultured human cell lines (K-562 and MIN-GL1) as well as their inhibitory effect on proliferation of phytohemagglutinin-stimulated human peripheral blood lymphocytes. The values of 50% inhibition of lymphocyte blastogenesis were very close to the 50% cytotoxic doses observed with the more sensitive cell line (MIN-GL1). T-2 toxin was the most cytotoxic with CD50 and ID50 values less than 1 ng/ml. Type A trichothecenes were the most cytotoxic followed by the type B trichothecenes; the non-trichothecenes were the least cytotoxic. The MTT cleavage test, in conjunction with cell culture, is a simple and rapid bioassay to evaluate cytotoxicity and immunotoxicity of Fusarium mycotoxins.

Monoclonal expansion of immunoglobulin not-secreting CD5+ CD11c+ CD38+ B-cells in a rare case of chronic lymphoplasmacytoid leukaemia.

We present the clinical and immunological features of a rare case of chronic lymphoid leukaemia with lymphoplasmacytoid morphology. The patient was first admitted suffering from weakness, pallor, dyspnoea, marked splenomegaly, hepatomegaly and systemic lymphadenopathy and panhypogammaglobulinaemia. White blood cell count revealed important leukocytosis (220 x 10(9) WBC/l) with 2% neutrophils and 98% lymphoid cells showing lymphoplasmacytoid features, while lymphoid cells of identical morphology severely infiltrated the bone marrow and lymph nodes. The disease, initially controlled by non aggressive chemotherapy over a period of 30 months, later evolved to a clinical and haematological picture suggestive of Richter's syndrome. Immunophenotyping of the leukaemic cells demonstrated a monoclonal expansion of B-cells bearing surface markers of typical CLL (CD5, CD19, CD20, CD21, CD22, CD23, CD24, CD40 and low density IgM+IgD/kappa) and also the CD11c and CD38 antigens. A proportion of these cells expressed activation markers (CD25, CD69 and CD71). Following in vitro activation with TPA or PWM, the cells responded by weak incorporation of 3H-TdR but failed to secrete immunoglobulins. These findings confirm the broad morphological, phenotypical and clinical spectrum of chronic lymphoid leukaemias.

Ontogeny of human lymphocytes. Two-color fluorescence analysis of circulating lymphocyte subsets in fetuses in the second trimester of pregnancy.

By using monoclonal antibodies, two-color immunofluorescence techniques and flow cytometry, we evaluated the surface marker phenotypes of lymphocyte subsets in cord blood samples from fetuses in the second trimester of pregnancy. The results indicate that cells of the T-, B- and NK-cell lineages as well as precursor cells can be detected in fetal blood at 18-20 weeks of gestation. At this stage of development, variable proportions of T and B lymphocytes express surface molecules, such as the CD1, CD10, CD38, CD45RA, indicative of a precursor or 'naive' state; on the other hand, the CD57 molecule is not detectable on the membrane of NK and T cells, and the RO isoform of the CD45 leukocyte antigen is synthesized by a low percentage of T cells. We suggest that the observed phenotypic peculiarities of the lymphoid cells might be related to the easy induction of tolerance that occurs in the early ontogenetic stages of the immune system.

Lymphocyte subpopulations in pediatric age. Definition of reference values by flow cytometry.

In the present paper we have analyzed the age-related changes in the distribution and numbers per cubic millimeter of the circulating lymphocyte subpopulations. Lymphocyte subsets have been examined by monoclonal antibodies specific for surface antigens (namely CD2, CD3, CD4, CD8, CD16, CD20 and CD57) and flow cytometry in lysed peripheral blood of normal neonates (1-3 days old), 1-6 month, 7-12 month, 1-2 year old babies and 3-5 year, 6-10 year old children and young people up to 17 years of age. The results confirm the lymphocytosis at birth and at later stages of life and indicate that major changes in the distribution of lymphocyte subsets occur during the first two years of life; namely we have observed sharp increase of circulating B lymphocytes and prevalence of CD4+ T lymphocytes with high CD4/CD8 ratios in babies up to two years of age, compared to the values observed in normal adults. Very few CD8+ CD57+ lymphocytes were present at birth; cells bearing this phenotype appeared later in life. Lymphocytes expressing the CD16 antigen were already present in newborns. The authors discuss the functional meanings of the age-related changes observed in the distribution and in the numbers of circulating lymphocytes. The presented data represent valuable normal ranges of lymphocyte subsets to compare with values observed in sick babies or children.